December 30, 2009

A German computer engineer said Monday that he had deciphered and published the secret code used to encrypt most of the world’s digital mobile phone calls, saying it was his attempt to expose weaknesses in the security of global wireless systems.

The action by the encryption expert, Karsten Nohl, aimed to question the effectiveness of the 21-year-old G.S.M. algorithm, a code developed in 1988 and still used to protect the privacy of 80 percent of mobile calls worldwide. The abbreviation stands for global system for mobile communication.

[...] The G.S.M. Association, the industry group based in London that devised the algorithm and represents wireless companies, called Mr. Nohl’s efforts illegal and said they overstated the security threat to wireless calls.

During an interview, Mr. Nohl said he took precautions to remain within legal boundaries, emphasizing that his efforts to crack the G.S.M. algorithm were purely academic, kept within the public domain, and that the information was not used to decipher a digital call.

[...] Mr. Nohl said the algorithm’s code book was available on the Internet through services like BitTorrent, which some people use to download vast quantities of data like films and music. He declined to provide a Web link to the code book, for fear of the legal implications, but said its location had spread by word of mouth.

[...] In a statement, the G.S.M. Association said efforts to crack the algorithm were more complex than critics have asserted, and that operators, by simply modifying the existing algorithm, could thwart any unintended surveillance.

The group said that hackers intent on illegal eavesdropping would need a radio receiver system and signal processing software to process raw radio data, much of which is copyrighted.

But Mr. Nohl, during a presentation Sunday to attendees at the Berlin conference, said the hardware and software needed for digital surveillance were available free as an open-source product in which the coding is available for individuals to tailor to their needs.